Silicon carbide film and method for manufacturing the same

ABSTRACT

There is disclosed a method for manufacturing a silicon carbide film in which a crystal orientation continued on a single crystal substrate surface and silicon carbide is allowed to epitaxially grow, the method comprising the steps of: entirely or partially providing the substrate surface with a plurality of undulations extended parallel in one direction; and allowing silicon carbide to grow on the substrate surface.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to a single crystal silicon carbide filmas an electronic material, particularly to silicon carbide which ispreferable in preparing a semiconductor device and which has a lowdefect density and to a method for manufacturing the silicon carbide.

(ii) Description of the Related Art

The growth of silicon carbide (SiC) has heretofore been classified to abulk growth by a sublimation process, and a thin film formation byepitaxial growth onto a substrate.

In the bulk growth by the sublimation process the growth of 6H—SiC or4H—SiC which is a polytypism with a high temperature phase is possible,and the preparation of SiC itself as the substrate has been realized.However, there are a large number of defects (micro pipes) introducedinto a crystal, and it has been difficult to enlarge a substrate area.

On the other hand, when the epitaxial growth process onto a singlecrystal substrate is used, the enhancement of controllability ofimpurity addition or the enlargement of substrate area, and thereduction of micro pipes having caused problems in the sublimationprocess are realized. In the epitaxial growth process, however, theincrease of a plane defect density by a difference in lattice constantbetween a substrate material and a silicon carbide film often raises aproblem. Particularly, since Si usually used as the substrate to growhas a large lattice mismatching from SiC, twins and anti phaseboundaries (APB) are remarkably generated in an SiC growth layer, andthese deteriorate the properties of SiC as an electronic element.

As a method of reducing surface defects in the SiC film, for example, atechnique of reducing the surface defects having inherent or morethickness is proposed in Japanese Patent Publication No. 41400/1994,which includes a process of disposing a growth area on a substrate togrow, and a process of allowing a silicon carbide single crystal to growin this growth area so that its thickness becomes the same as or morethan the thickness inherent to the growth surface orientation of thesubstrate. However, since two orientations of anti phase boundariescontained in SiC have properties to be enlarged in directions orthogonalto each other with respect to the increase of SiC film thickness, theanti phase boundaries cannot effectively be reduced. Furthermore, thedirection of a super structure formed on the grown SiC surface cannotarbitrarily be controlled. Therefore, for example, when the separatedgrowth areas are combined with each other according to the growth, theanti phase boundary is newly formed on this combined part, whichdeteriorates electric properties.

As a method of effectively reducing the anti phase boundaries, K.Shibahara et al. have proposed a growth process onto an Si (100) surfacesubstrate in which a surface normal axis is slightly inclined to [110]from [001] direction (an off angle is introduced) (Upright PhysicsLetter, vol. 50, 1987, page 1888). In this method, since an atomic levelstep is introduced at equal intervals in one direction by applying theslight inclination to the substrate, the surface defect having adirection parallel to the introduced step is propagated. On the otherhand, the propagation of the surface defect to the direction vertical tothe introduced step (a direction across the step) is effectivelysuppressed. Therefore, since the anti phase boundary enlarged in thedirection parallel to the introduced step is enlarged in preference tothe anti phase boundary enlarged in the orthogonal direction in the twoorientations of anti phase boundaries included in the film with respectto the film thickness increase of silicon carbide, the anti phaseboundaries can effectively be reduced. However, as shown in FIG. 1, inthis method, the increase of step density of an SiC/Si interface causesthe generation of an undesired anti phase boundary 1, and there is aproblem that the anti phase boundary cannot completely be eliminated.Additionally, in FIG. 1, numeral 1 denotes an anti phase boundarygenerated in the single atom step of Si substrate, 2 denotes an antiphase boundary association point, 3 denotes an anti phase boundarygenerated in an Si substrate surface terrace, θ denotes an off angle,and φ denotes an angle (54.7°) formed between the Si (001) surface andthe anti phase boundary. The anti phase boundary 3 generated in the Sisubstrate surface terrace disappears in the anti phase boundaryassociation point 2, but the anti phase boundary 1 generated in thesingle atom step of the Si substrate has no other boundary to associate,and does not disappear,

SUMMARY OF THE INVENTION

The present invention has been developed under the above-describedbackground, and an object thereof is to provide a silicon carbide filmin which anti phase boundaries are effectively reduced or eliminated.

To attain the above-described object, the present invention provides thefollowing constitutions.

(Constitution 1) A method for manufacturing a silicon carbide film inwhich a crystal orientation is inherited on a single crystal substratesurface and silicon carbide is allowed to epitaxially grow, the methodfor manufacturing the silicon carbide film comprising the steps of:entirely or partially providing the substrate surface with a pluralityof undulations extended parallel in one direction; and allowing siliconcarbide to grow on the substrate surface.

(Constitution 2) The method for manufacturing the silicon carbide filmin the constitution 1 in which during the growth of the silicon carbidefilm, an epitaxial growth mechanism is used so that a propagationorientation of a surface defect generated in the film can be limited ina specified crystal surface.

(Constitution 3) The method for manufacturing the silicon carbide filmdescribed in the constitution 1 or 2 in which when an average value ofan interval between undulation tops of the substrate surface is set toW, the silicon carbide film has a thickness of W/2(=2^(½)) or more.

(Constitution 4) The method for manufacturing the silicon carbide filmdescribed in the constitutions 1 to 3 in which the interval between theundulation tops of the substrate surface is in a range of 0.01 μm to 10μm, an undulation height difference is in a range of 0.01 μm to 20 μm,and the inclination degree of an inclined surface in the undulation isin a range of 1° to 55°.

(Constitution 5) The method for manufacturing the silicon carbide filmdescribed in the constitutions 1 to 4 in which the substrate comprises asingles crystal Si, the substrate surface comprises a (001) surface, andthe surface is provided with the undulation extended in parallel with a[110] orientation.

(Constitution 6) The method for manufacturing the silicon carbide filmdescribed in the constitutions 1 to 4 in which the substrate comprises asingle crystal 3C—SiC, the substrate surface comprises a (001) surface,and the surface is provided with the undulation extended in parallelwith a [110] orientation.

(Constitution 7) The method for manufacturing the silicon carbide filmdescribed in the constitutions 1 to 4 in which the substrate comprises ahexagonal single crystal SiC, the substrate surface comprises a (1, 1,−2, 0) surface, and the surface is provided with the undulation extendedin parallel with a [1, −1, 0, 0] orientation or a [0, 0, 0, 1]orientation.

(Constitution 8) A silicon carbide film manufactured using the methoddescribed in the constitutions 1 to 7.

(Constitution 9) The silicon carbide film which comprises a step of aplurality of undulations entirely or partially formed on a singlecrystal substrate surface and extended parallel in one direction, andwhich has a structure subjected to epitaxial growth in a method so thata propagation orientation of a film inner surface defect can be limitedin a specified crystal surface.

According to the constitution 1, by providing the surface of thesubstrate to grow of silicon carbide with a plurality of undulationsextended parallel in one direction, the effect of introducing the offangle proposed by K. Shibahara et al. can be obtained in the inclinedsurface of each undulation. Furthermore, in the present invention, sincethe steps oriented in a Plane symmetrical orientation are introduced tothe surface of the substrate to grow of silicon carbide with astatistically balanced density, the anti phase boundaries in theundesirably introduced silicon carbide layer, which generated by thesteps on the surface of the substrate, are effectively annihilated, andthe silicon carbide film in which the anti phase boundaries arecompletely eliminated can be obtained. Moreover, in the presentinvention, the individual growth areas form the same phase area enlargedin the same direction by the off angle introducing effect. Therefore,even when the separated growth areas are combined with one anotheraccording to the growth, there is an advantage that no anti phaseboundary is produced in the combined part.

Additionally, the undulation mentioned in the present invention does notrequire a parallel property or a mirror surface symmetrical relation ina mathematically strict meaning, and may have a configuration enough toeffectively reduce or eliminate the anti phase boundaries.

Examples of the method of forming an undulation shape on the substrateto grow include a photolithography technique, a press processingtechnique, a laser processing or ultrasonic processing technique, anabrasion processing technique, and the like. Even when any of themethods is used, the final configuration of the surface of the substrateto grow may have a sufficient configuration to such an extent that theanti phase boundaries can effectively be reduced or eliminated.

When the photolithography technique is used, the arbitrary undulationshape can be transferred to the substrate to grow by arbitrarily forminga mask pattern to be transferred to the substrate. The width of theundulation shape can be controlled, for example, by changing a patternlinear width. Moreover, the depth of the undulation shape or the angleof the inclined surface can be controlled by controlling the etchingselection ratio of resist and substrate. Even when a rectangular patternshape is not required, the undulation pattern with an undulatory shapecan be formed by performing a thermal treatment to soften the resistafter transferring the pattern to the resist.

When the press processing technique is used, an arbitrary undulationshape can be formed onto the substrate to grow by arbitrarily forming apressing mold. The undulation with various shapes can be formed on thesubstrate to grow by forming various shapes of molds.

When the laser or ultrasonic processing technique is used, theundulation shape is directly processed/formed on the substrate, whichenables a fine processing.

When the abrasion processing is used, the width or depth of theundulation shape can be controlled by changing the magnitude of abrasivegrain diameter or the processing pressure during the abrasion. When thesubstrate provided with the one-direction undulation shape i,i prepared,the abrasion is performed only in one direction.

According to the constitution 2, the effect of the constitution 1 cansecurely and sufficiently be obtained by performing the epitaxial growthunder the growth condition so that the propagation orientation of thefilm inner surface defect can be limited in the specified crystalsurface. For example, a step flow growth can satisfy this growthcondition.

According to the constitution 3, when the average value of the intervalbetween the undulation tops of the surface of the substrate to grow ofsilicon carbide is set to W, the silicon carbide film has a thickness ofW/2(=2^(½)). At this time, all the anti phase boundaries disappear.Therefore, it is preferable to set the thickness of the silicon carbidefilm to W/2(=2^(½)) or more.

Additionally, to obtain the effect of the present invention with a thinfilm thickness, the interval between the undulation tops is preferablynarrower.

In the constitution 4, the internal of the undulation tops, theundulation height difference, and the inclination degree of theundulation are defined.

The interval of the undulation tops is preferably 0.01 μm or more fromthe standpoint of the limitation of the fine processing technique in thepreparation of the undulation to the substrate to grow. Moreover, whenthe interval of the undulation tops exceeds 10 μm, the frequency of theassociation of the anti phase boundaries is excessively lowered.Therefore, the interval of the undulation tops is preferably 10 μm orless. When the undulation top interval is more preferably in a range of0.1 μm to 3 μm, the effect of the present invention is sufficientlyfulfilled.

The height difference and interval of the undulation influence theundulation inclination degree, that is, the step density. Since apreferable step density changes with the crystal growth conditions, thiscannot absolutely be said, but the usually necessary undulation heightdifference has substantially the same degree as the undulation topinterval, that is, a range of 0.01 μm to 20 μm.

The effect of the present invention is fulfilled by promoting the growthof silicon carbide in the vicinity of the atomic level step in thesurface of the substrate to grow. Therefore, the present invention isrealized when the undulation inclination degree is in an inclination of54.70° or less of the (111) surface in which the entire inclined surfaceis covered with the single step. Moreover, since the undulation inclinedsurface step density remarkably decreases in the inclination degree lessthan 1°, the inclination degree of the undulation inclined surface ispreferably 1° or more. When the inclination angle of the inclinedsurface of the undulation is more preferably in a range of 2° to 10°,the effect of the present invention is sufficiently fulfilled.

Additionally, the “undulation inclined surface” mentioned in the presentinvention includes various configurations such as a flat plane and acurved plane. Moreover, the “inclination degree of the inclined surfacein the undulation” means the substantial inclination degree of theinclined surface which contribute to the effect of the presentinvention, and the maximum inclination degree, average inclinationdegree, and the like can be employed as the “inclination degree of theundulation” in accordance with the configuration of the inclinedsurface.

In the constitutions 5 to 7, the surface orientation of the surface ofthe substrate to grow of silicon carbide, and the undulation orientationare defined.

When the single crystal Si (001) surface or the cubic silicon carbide(001) surface of the single crystal is used as the surface orientationof the surface of the substrate to grow on which the cubic or hexagonalsilicon carbide is allowed to grow, the propagation direction of theanti phase boundary is [110]. Therefore, as shown in FIG. 2, byarranging the undulation of the surface in parallel with any one of thedirections ([1, −1, 0] direction in FIG. 2), the silicon carbide filmcan be obtained in which the anti phase boundaries are effectivelyeliminated on the axis orthogonal to the undulation shown in FIG. 3(Constitutions 5, 6). Additionally, in FIG. 3, character W denotes theundulation top interval.

When the hexagonal SiC (1, 1, −2, 0) surface of the single crystal isused as the surface orientation of the surface of the substrate to growon which the cubic or hexagonal silicon carbide is allowed to grow, thepropagation direction of the anti phase boundary is [1, −1, 0, 0], [−1,1, 0, 0], [0, 0, 0, 1], [0, 0, 0, −1]. Therefore, by arranging theundulation of the surface in parallel with any one of the directions,the silicon carbide film can be obtained in which the anti phaseboundaries are effectively eliminated as described above (Constitution7).

According to the constitution 8, by using the method described in theconstitutions 1 to 7, the silicon carbide film can be obtained in whichthe anti phase boundaries are effectively reduced or eliminated.

The silicon carbide film of the present invention has a very superiorelectric property due to a low crystal boundary density, and canpreferably be used as electronic elements such as a semiconductorsubstrate and a crystal growing substrate (including a seed crystal).

According to the constitution 9, by using the substrate structure andcrystal growing method, the silicon carbide film can be obtained inwhich the anti phase boundaries are effectively reduced or eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing the generation orextinction of anti phase boundaries with the growth of 3C—SiC onto an Sisubstrate to which an off angle is applied.

FIG. 2 is a perspective view showing a single crystal Si (001) surfacesubstrate provided with an undulation parallel to [1, −1, 0]orientation.

FIG. 3 is a schematic sectional view showing the extinction of the antiphase boundaries with the growth of 3C—SiC onto the Si (001) surfacesubstrate provided with the undulation.

FIG. 4 is a scanning electron microscope image of an SiC film surfacedeveloped on the substrate with an off angle of 4°.

FIG. 5 is a scanning electron microscope image of the SiC film surfacedeveloped on the substrate with no off angle.

FIG. 6 is a scanning electron microscope image of the Si substrateprovided with the undulation.

FIG. 7 is a schematic perspective view showing the Si substrateprocessed when the direction of an undulation pattern deviates from[110] orientation.

FIG. 8 is a schematic sectional view showing the Si substrate surfaceprovided with a saw blade shaped undulation.

FIG. 9 is a schematic sectional view showing a method of preparing theundulation in a process other than etching.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will more concretely be described hereinafterbased on examples.

Comparative Example

First, to confirm the effect by the introduction of the off angle, an Si(001) surface with no off angle, and Si (001) surfaces with off anglesof 4° and 10° were prepared as the substrates to grow, and the growingof SiC (3C—SiC) was performed. The growing of SiC is divided to aprocess of carbonizing the substrate surface, and an SiC growing processby alternate supply of source gas. In the carbonizing process, theprocessed substrate was heated in an acetylene atmosphere to 1050° C.from a room temperature for 120 minutes. After the carbonizing process,the substrate surface was alternately exposed to dichlorosilane andacetylene in 1050° C., and the growing of SiC was carried out. Thedetailed conditions of the carbonizing process are shown in Table 1, andthe detailed conditions of the SiC growing process are shown in Table 2.

TABLE 1 Carbonizing temperature 1050° C. Acetylene introducingtemperature  24° C. Acetylene flow rate  10 sccm Pressure  20 mTorrTemperature rise time 120 minutes

TABLE 2 Growing temperature 1050° C. Gas supply method Alternate supplyof acetylene and dichlorosilane Acetylene flow rate   10 sccmDichlorosilane flow rate   10 sccm Gas supply interval   5 sec Gassupply time   10 sec Maximum pressure  100 mTorr Minimum pressure   10mTorr No. of gas supply cycles 50000 times SiC film thickness 4.5 μm to5.9 μm

When the density of the anti phase boundary was measured with respect tothe SiC developed on each substrate, results shown in Table 3 wereobtained.

Additionally, the density of the anti phase boundary was obtained by AFMobservation of the silicon carbide surface. In this case, afterperforming a thermal oxidation treatment on the silicon carbide surfaceand further removing a thermally oxidized film to expose the anti phaseboundary, the observation was performed.

TABLE 3 Off angle (degrees) Anti phase boundary density (cm⁻²) 0° 8 ×10⁹ 4° 2 × 10⁸ 10°  1 × 10⁹

From the relationship between the off angle and the anti phase boundarydensity shown in Table 3, the decrease of the anti phase boundarydensity by the off angle introduction is confirmed, but it is seen thatcomplete elimination is not realized.

The scanning electron microscope image of the SiC film surface developedon the substrate with the off angle of 4° is shown in FIG. 4, and thescanning electron microscope image of the SiC film surface developed onthe substrate with no off angle is shown in FIG. 5.

From FIGS. 4 and 5, the enlargement of the terrace area by the off angleintroduction is confirmed and it is seen that the SiC growth in the stepflow mode is dominant and that the propagation orientation of thesurface defect is limited in the specified crystal surface.

EXAMPLE 1

After preparing an Si (001) surface as the substrate to grow, andthermally oxidizing the substrate surface, the photolithographytechnique was used to form a line and space pattern with a width of 1.5μm, length of 60 mm, and thickness of 1 μm in a resist on the substratesurface. Additionally, the direction of the line and space pattern wasset to be parallel to the [110] orientation. By using a hot plate on theconditions shown in Table 4 to heat this substrate, the line and spaceresist pattern was extended and deformed in the direction orthogonal toa line, and a resist pattern shape with a section having an undulatoryshape was obtained in which the undulation top and bottom were connectedvia a smooth curve. The sectional shape (undulation) and flat shape(line and space) of this resist pattern were transferred to the Sisubstrate by dry etching.

After removing the resist in a mixed solution of hydrogen peroxide andsulfuric acid (FIG. 6), the growing of 3C—SiC was carried out. Thegrowing of SiC is divided to the process of carbonizing the substratesurface, and the SiC growing process by the alternate supply of thesource gas. The detailed conditions of the SiC growing process are shownin Table 5. Additionally, the detailed conditions of the carbonizingprocess are similar to those of Table 1.

TABLE 4 Heating temperature 170° C. Heating time 10 minutes

TABLE 5 Growing temperature 1050° C. Gas supply method Alternate supplyof acetylene and dichlorosilane Acetylene flow rate  10 sccmDichlorosilane flow rate  10 sccm Gas supply interval  5 sec Gas supplytime  10 sec Maximum pressure 100 mTorr Minimum pressure  10 mTorr No.of gas supply cycles 100 to 50000 times

When the density of the anti phase boundary appearing on the uppermostsurface was measured in a similar manner as above by changing the numberof source gas supply cycles to change the film thickness of SiC in theSiC growing process, results shown in. Table 6 were obtained.

TABLE 6 Film thickness (μm) Anti phase boundary density (cm⁻²) 0.1 5 ×10⁹ 0.4 6 × 10⁷ 1.0 1 × 10⁵ 1.8 7 × 10³ 2.5 85 3.5 11 5.5  0

It is seen from the relationship between the SiC film thickness and theanti phase boundary density shown in Table 6 that when the SiC filmthickness subjected to the epitaxial growth on the Si substrate havingan undulation shape exceeds 2.1 μm being 1/2 times the undulation topinterval of 3.0 μm, the decrease of the anti phase boundary isremarkable, and that the effectiveness of the present invention isremarkable as compared with the numeric values of the conventionalprocess shown in Table 3.

EXAMPLE 2

The Si (001) surface was prepared as the substrate to grow, and thephotolithography technique was used to form the line and space patternwith a width of 1.5 μm, length of 60 mm, and thickness of 1 μm in theresist on the substrate surface. Additionally, the direction of the lineand space pattern was set to be parallel to the [110] orientation. Byusing the hot plate on the conditions shown in Table 7 to heat thesubstrate and soften the resist, the sectional shape of the resist,pattern was changed. The sectional shape (undulation) and flat shape(line and space) of this resist pattern were transferred to the Sisubstrate by dry etching.

After removing the resist in the mixed solution of hydrogen peroxide andsulfuric acid, the growing of 3C—SiC was carried out. The growing of SiCis divided to the process of carbonizing the substrate surface, and theSiC growing process by the alternate supply of the source gas.Additionally, the detailed conditions of the carbonizing process wereset to be similar to those of Table 1, and the detailed conditions ofthe SiC growing process were set to be similar to those of Table 5.

TABLE 7 Heating temperature 150° C. to 200° C. Heating time 10 minutes

When the density of the anti phase boundary appearing on the uppermostsurface was measured in a similar manner as above with respect to 3C—SiCdeveloped on each substrate by changing the heating temperature of theresist pattern between 150° C. and 200° C. to change the undulationinclination angle θ, results shown in Table 8 were obtained.

TABLE 8 Undulation inclination Anti phase boundary density angle(degrees) (cm⁻²)  0° 8 × 10⁹ 0.2°  3 × 10⁹ 0.5°  1 × 10⁹  1°  30  2°  0 4°  0 10°  45 40° 230 50° 320 60° 1 × 10⁴ 70° 7 × 10⁵ 90° 5 × 10⁹

From the relationship between the undulation inclination degree and theanti phase boundary density shown in Table 8, when the undulationinclination angle θ is particularly less than the angle formed by the(111) surface of 54.7° and equal to or more than 1°, the decrease of theanti phase boundary density can be confirmed. Furthermore, as comparedwith the numeric values of the conventional process shown in Table 3,even with the same off angle, in the 3C—SiC developed on the undulationprocesses substrate as in the present invention, the anti phase boundarydensity remarkably decreases or disappears, and it is seen that theeffectiveness of the present invention is remarkable.

EXAMPLE 3

The Si (001) surface was prepared as the substrate to grow, and thephotolithography technique was used to form the line and space patternwith a width of 1.5 μm, length of 60 mm, and thickness of 1 μm in theresist on the substrate surface. Additionally, with respect to thedirection of the line and space pattern, the crossed axes angle ω of the[110] orientation and the line and space pattern direction (see FIG. 7)was changed as shown in Table 9. Thereafter, by using the hot plate onthe conditions shown in Table 4 to heat the substrate and soften theresist, the sectional shape of the resist pattern was changed. Theresist pattern shape was transferred to the Si substrate by dry etching.

After removing the resist in the mixed solution of hydrogen peroxide andsulfuric acid, the growing of 3C—SiC was carried out. The growing of SiCis divided to the process of carbonizing the substrate surface, and theSiC growing process by the alternate supply of the material gas.Additionally, the detailed conditions of the carbonizing process wereset to be similar to those of Table 1, and the detailed conditions ofthe SiC growing process were set to be similar to those of Table 2.

When the density of the anti phase boundary appearing on the uppermostsurface was measured in a similar manner as above with respect to the3C—SiC developed on each substrate by changing the crossed axes angle ω,results shown in Table 9 were obtained.

TABLE 9 Crossed axes angle Anti phase boundary density (degrees) (cm⁻²) 0° 0 15° 12 30° 200 45° 850

From the relationship between the crossed axes angle ω and the antiphase boundary density shown in Table 9, when the direction of the lineand space pattern is oriented in the [110] orientation, the decrease ofthe anti phase boundary density can be confirmed. Furthermore, ascompared with the numeric values of the conventional process shown inTable 3, it is seen that the anti phase boundary density is remarkablydecreased or eliminated, and that the effectiveness of the presentinvention is remarkable.

EXAMPLE 4

In the examples 1 to 3, the mask having the line and space pattern inwhich the line width is equal to the space width was used, the substratehaving the undulation sectional pattern in which the ratios of recessesand protrusions were equal to each other was prepared, and the growingof 3C—SiC was performed on the substrate. On the other hand, in theexample 4, the line and space patterns with a line width of 1.5 μm, andspace widths which are twice, four times, eight times, and 16 times theline width were used as the pattern with the decreased density ofprotrusions to perform a substrate processing, and the growing of 3C—SiCwas performed on the substrate. Both the substrate processing conditionsand the SiC growing conditions are the same as those of the example 3.Additionally, the undulation inclination angle was set to 4°.

When the anti phase boundary density was measured similarly to the abovewith respect to the patterns by changing the density of undulationrecesses, results shown in Table 10 were obtained. Additionally, ascomparative examples, the anti phase boundary density with the use ofthe pattern having a line width and a space width both of 1.5 μm, andthe anti phase boundary density with the use of the Si (001) substrate(off angle 0°) with no undulation in which the line width is extended toinfinity (∞) and supposedly to the limit were similarly measured asshown in Table 10.

TABLE 10 Ratio of space Anti phase boundary width/line width density(cm⁻²) 1  0 2  12 4 165 8 890 16  2 × 10⁴ ∞ 8 × 10⁹

From Table 10, when the undulation protrusion interval increases, andthe undulation density decreases, the increase of the anti phaseboundary density can be confirmed. Furthermore, as compared with thenumeric values of the conventional process of Table 3, it is seen thatthe anti phase boundary density is remarkably decreased or eliminated,and that the effectiveness of the present invention is remarkable.

EXAMPLE 5

In the examples 1 to 4 only the undulatory structure of the substratesection has been described. It is apparent also from the description ofFIG. 3 that the effectiveness of the present invention can also be heldwith respect to the structure other than the undulatory type. Actually,the undulation processing with the saw blade shaped section was appliedto the Si (001) surface in the following method, and the growing of3C—SiC was performed on the substrate.

Specifically, the Si (001) surface was prepared as the substrate togrow, and the photolithography technique was used to form the line andspace pattern with a width of 1.5 μm, length of 60 mm, and thickness of1 μm in the resist on the substrate surface. Additionally, the directionof the line and space pattern was set to be parallel to the [110]orientation. The resist pattern shape was transferred to the Sisubstrate by dry etching. After removing the resist in the mixedsolution of hydrogen peroxide and sulfuric acid, the substrate wasimmersed in KOH aqueous solution to perform wet etching. The conditionsof wet etching are shown in Table 11. As a result of the wet etching,the single crystal Si (001) surface having the saw blade shapedundulation with an inclination angle of 1°, 10°, 55° was obtained (seeFIG. 8). Additionally, in FIG. 8, numeral 4 denotes the substratesectional structure before the wet etching, and 5 denotes the saw bladeshaped substrate sectional structure after the wet etching.

TABLE 11 Etching solution KOH aqueous solution Solution density 15mol/cc Temperature 60° C. Time 5 minutes, 10 minutes, 20 minutes

The growing of 3C—SiC was carried out on the above-described substrate.The growing of SiC is divided to the process of carbonizing thesubstrate surface, and the SiC growing process by the alternate supplyof the source gas. Additionally, the detailed conditions of thecarbonizing process were set to be similar to those of Table 1, and thedetailed conditions of the SiC growing process were set to be similar tothose of Table 2.

When the density of the anti phase boundary appearing on the uppermostsurface was measured in a similar manner as above with respect to SiCdeveloped on each substrate, results shown in Table 12 were obtained.

TABLE 12 Undulation inclination angle Anti phase boundary density(degrees) (cm⁻²)  1° 140 10°  30 55° 420

It is seen from Table 12 that even when the substrate section has a sawblade shaped undulation structure, the present invention has aneffectiveness. Moreover, this substrate preparing method is suitable infulfilling the effectiveness of the present invention.

EXAMPLE 6

In each of the examples 1 to 5 the cubic silicon carbide film wasdeveloped on the Si (001) surface substrate. In the example 6, as thesubstrate to grow, a substrate provided with the undulation extended inparallel with the [110] orientation on the (001) surface of thesingle-crystal cubic silicon carbide (single crystal 3C—SiC), and asubstrate provided with the undulation extended in parallel with the [0,0, 0, 1] orientation on the (1, 1, −2, 0) surface of the single-crystalhexagonal silicon carbide were used, and the growing of the cubicsilicon carbide film or the hexagonal silicon carbide film was performedon each substrate surface.

As a result, the effectiveness of the present invention was confirmedsimilarly to the examples 1 to 5.

EXAMPLE 7

In each of the examples 1 to 6 the method of using the lithographytechnique to etch the Si substrate (001) surface is employed as themethod of preparing the undulation, but the method of preparing theundulation on the surface of the substrate to grow can be performed inthe technique other than etching to bring about the effectiveness of thepresent invention. One example will be described in the example 7.

By using the Si (001) surface as the substrate, and thermally oxidizingthe surface, an Si oxidized film (SiO₂ film) of 3000 angstroms wasformed. Subsequently, the photolithography technique was used to formthe line and space pattern with a width of 1.5 μm, length of 60 mm, andthickness of 1 μm in the resist on the thermally oxidized film.Additionally, the direction of the line and space pattern was set to beparallel to the [110] orientation. The resist pattern shape wastransferred to the thermally oxidized film by dry etching, and the SiO₂pattern and Si exposed portion were arranged in a stripe shape. Afterremoving the resist in the mixed solution of hydrogen peroxide andsulfuric acid, the selective homo-epitaxial growth of Si was carried outon this substrate as shown in FIG. 9. The detailed conditions of the SiCgrowing process are shown in Table 13. Additionally, in FIG. 9, numeral6 shows the striped SiO₂ pattern, and 7 shows the Si layer resultingfrom the selective homo-epitaxial growth.

TABLE 13 Growing temperature 1000° C. Hydrogen flow rate  50 sccmDichlorosilane flow rate  10 sccm Maximum pressure 100 mTorr

As a result of the Si growth, the single crystal Si (001) surfaceprovided with the undulation of the inclination angle 55° was obtained.The growing of 3C—SiC was performed on this substrate surface, and itwas confirmed that the anti phase boundary density remarkably decreased.

EXAMPLE 8

In the example 8, it was tried to prepare the substrate with theundulation parallel to the [110] direction formed thereon in a method ofperforming an abrasion processing on the Si (100) substrate surface inparallel with the [110] direction. In the abrasion, a commercial diamondslurry with a diameter of about 15 μmφ(manufactured by Engis Co.: HighPress) and a commercial abrasion pad (manufactured by Engis Co.: M414)were used.

By allowing the diamond slurry to uniformly permeate on the pad, placingthe Si (100) substrate on the pad, applying a pressure of 0.1 to 0.2kg/cm² to the entire Si (100) substrate, and reciprocating the substrate300 times for a distance of about 20 mm on the pad in parallel with the[110] orientation, the one-direction abrasion processing was performed.An infinite number of abrasion scratches were formed in parallel withthe [110] direction on the Si (100) substrate surface.

Since the abrasive grains, and the like adhered to the Si (100)substrate surface subjected to the one-direction abrasion processing,the substrate surface was washed in an NH₄OH+H₂O₂+H₂O mixed solution (ata ratio of NH₄OH:H₂O₂:H₂O=4:4:1 and a solution temperature of 60° C.),alternately immersed and washed in an H₂SO₄+H₂O₂ solution (at a ratio ofH₂SO₄:H₂O₂=1:1 and a solution temperature of 80° C.) and in an HF (10%)solution three times each, and finally rinsed with de-ionized water.

After washing, a thermally oxidized film was formed in a thickness ofabout 5000 angstroms on the one-direction abrasion processed substrate.The thermally oxidized film was removed by the HF 10% solution. Whenonly the abrasion is performed, there are a large number of finerecesses/protrusions and defects in addition to scratches on thesubstrate surface, and the substrate cannot be used as the substrate togrow. However, by once forming the thermally oxidized film, and removingthe thermally oxidized film anew, the fine recesses/protrusions of thesubstrate surface were removed, and a very smooth undulation surfacecould be obtained. When the undulatory section is observed, themagnitude of the undulatory recess/protrusion is unstable and irregular,but the density is high. At least a horizontal surface does not exist.The surface is constantly in an undulation state. On average, the groovedepth was in a range of 30 to 50 nm, and the width was in a range ofabout 0.5 to 1.5 μm. The inclination degree was in a range of 3 to 5degrees.

This substrate was used to form the SiC film on the substrate. As aresult, the effect of the substrate with the undulation parallel to[110] formed thereon could be obtained. Specifically, the defects of theanti phase boundary remarkably decrease.

For example, the anti phase boundary density of the SiC film developedon the non-abraded Si substrate is 8×10⁹ boundaries/cm², while the antiphase boundary defect density of the SiC film developed on the Sisubstrate subjected to this one-direction abrasion is 0 to 1 defect/cm².The undulation shape and anti phase boundary defect density with respectto the abrasive grain size are as shown in Table 14. Moreover, theundulation density and anti phase boundary defect density with respectto the number of abrasions are as shown in Tables 15.

TABLE 14 Depth/width Inclination Anti phase Abrasive grain (betweendegree boundary size (μmφ) protrusions) (nm) (degrees) density (cm⁻²) 3 7/500 1 30 9 10/500 2 0 15 35/1000 4 0

(The conditions described in the example 8 were used and only theabrasive grain size was changed.)

TABLE 15 No. of abrasion/ Undulation Anti phase boundary reciprocation(times) density (%) density (cm⁻²) 50 50 100 100 80 20 300 100 0

(The conditions described in the example 8 were used and only the numberof reciprocation was changed.)

Additionally, in the example 8, the diamond slurry with a size of 15 μmφwas used as the abrasive, but the abrasive grain size and type are notlimited. Moreover, the pad is not limited to the above. Furthermore, theload pressure between the substrate and the pad during abrasion, theabrasion speed and times, and the like are not limited to the above.Moreover, Si (100) was used in the example 8, but even when the cubicSiC, or hexagonal SiC is used, needless to say, the results similar tothe above-described results can be obtained.

The examples have been illustrated to describe the present invention,but the present invention is not limited to the above-describedexamples.

For example, the film formation conditions, thickness, and the like ofthe silicon carbide film are not limited to those of the examples.

Moreover, for example, the single crystal substrates such as siliconcarbide and sapphire can be used as the substrate to grow.

As the source gas of silicon, dichlorosilane (SiH₂Cl₂) was used, butsilane compound gases such as SiH₄, SiCl₄, and SiHCl₃ can be used.Moreover, as the source gas of carbon, acetylene (C₂H₂) was used, buthydrocarbon gases such as CH₄, C₂H₆, and C₃H₈ can be used.

Additionally, the epitaxial growth process of silicon carbide is notlimited as long as the propagation orientation of the film inner surfacedefect can be limited in the specified crystal surface, and in additionto a gas phase chemical deposition (CVD) process, a liquid phaseepitaxial growth process, a sputtering process, a molecular beam epitaxy(MBE) process, and the like can be used. Moreover, in the CVD process,instead of the alternate supply process of the material gas, asimultaneous supply process of material gas can be used.

For the silicon carbide film formed on the substrate to grow by theabove-described method of the present invention, by joining the siliconcarbide film surface to an insulator, removing the substrate to grow,then removing the defective layer of the silicon carbide film (a parthaving an anti phase boundary density on the side of the substrate togrow), a semiconductor-on-insulator (SOI) structure can be obtained inwhich a semiconductor thin film is formed on the insulator.

Here, the joining of the silicon carbide film and the insulator can beperformed by methods such as anodic bonding, bonding by a low meltingglass, direct bonding, and bonding by an adhesive. The anodic bondingmethod comprises placing a glass containing an electric charge movableion (e.g., silicate glass, borosilicate glass, borate glass,aluminosilicate glass, phosphate glass, fluorophosphate glass, and thelike) in contact with the silicon carbide film, and applying an electricfield to perform the bonding. In this case, the bonding temperature isin a range of 200 to 300° C., the applied voltage is in a range of 500to 1000 V, and the load is in a range of about 500 to 1000 g/cm². Thebonding method by the low melting glass comprises depositing the lowmelting glass on the silicon carbide film surface by the sputteringprocess or the like, applying a load and heat, and bonding the glassesto each other. The direct bonding method comprises contacting andconnecting the silicon carbide film directly to the glass by anelectrostatic force, and subsequently applying the load and heat tostrengthen the connection in the interface.

The substrate to grow can be removed, for example, by wet etching. Forexample, the silicon substrate is removed by immersing the substrate ina mixed acid of HF and HNO₃ (HF:HNO₃=7:1).

The defective layer is removed for the purpose of removing the defectivelayer in which the anti phase boundaries exist with a high density inthe vicinity of the substrate interface of the silicon carbide film. Thedefective layer can be removed, for example, by dry etching. Forexample, by using CF₄ (40 sccm) or O₂ (10 sccm) as an etching gas, andperforming a reactive ion etching at RF power of 300 W.

The SOI structure unit (substrate) is applied, for example, to asemiconductor substrate, a transparent conductive film in the substratefor TFT liquid crystal, a dielectric layer for a Kerr effect in anoptical magnetic recording medium, a micro machine, various sensors(pressure sensor, and the like), an X-ray penetrable film, and the like.

As described above, according to the method of manufacturing siliconcarbide of the present invention, the silicon carbide film can beobtained in which the anti phase boundaries are effectively reduced oreliminated.

Moreover, since the crystal boundary density is small, the siliconcarbide film of the present invention has a very superior electricproperty, and can extensively be used as various electronic elements,and the like.

What is claimed is:
 1. A method for manufacturing a silicon carbide filmin which a crystal orientation is inherited on a single crystalsubstrate surface and silicon carbide is allowed to epitaxially grow,the method comprising the steps of: entirely or partially providing saidsubstrate surface with a plurality of undulations extended parallel inone direction, each of said undulations being formed in a manner suchthat inclined surfaces thereof with an angle smaller than 90° relativeto a basal plane are opposed to each other and an integral value of theangles of inclined surfaces is substantially 0°; and allowing thesilicon carbide to grow on the substrate surface.
 2. The method formanufacturing the silicon carbide film according to claim 1 wherein thesilicon carbide is grown in a manner such that surface defects caused inthe silicon carbide film can be limited to propogate towards specificcrystal surface orientations.
 3. The method for manufacturing thesilicon carbide film according to claim 1 wherein when an average valueof an interval between undulation tops of said substrate surface to setto W, the silicon carbide film has thickness of W/{square root over(2)}[(=2^(½))] or more.
 4. The method for manufacturing the siliconcarbide film according to claim 1 wherein the interval between theundulation tops of said substrate surface is in a range of 0.01 μm to 10μm, an undulation height difference is in a range of 0.01 μm to 20 μm,and an inclination degree of an inclined surface in the undulation is ina range of 1° to 55°.
 5. The method for manufacturing the siliconcarbide film according to claim 1 in which a crystal orientation isinherited on a single crystal substrate surface and silicon carbide isallowed to epitaxially grow, the method for manufacturing the siliconcarbide film comprising steps of: entirely or partially providing saidsubstrate surface with a plurality of undulations extended parallel inone direction; and allowing silicon carbide to grow on the substratesurface, wherein said substrate comprises a single crystal 3C—SiC, thesubstrate surface comprises a (001) surface, and the surface is providedwith the undulation extended in parallel with a [110] orientation. 6.The method for manufacturing the silicon carbide film according to claim1 in which a crystal orientation is inherited on a single crystalsubstrate surface and silicon carbide is allowed to epitaxially grow,the method for manufacturing the silicon carbide film comprising stepsof: entirely or partially providing said substrate surface with aplurality of undulations extended parallel in one direction; andallowing silicon carbide to grow on the substrate surface, wherein saidsubstrate comprises a hexagonal single crystal SiC, the substratesurface comprises a (1, 1, −2, 0) surface, and the surface is providedwith the undulation extended in parallel with a [1, −1, 0, 0]orientation or a [0, 0, 0, 1] orientation.
 7. A silicon carbide filmmanufactured using the method according to claim
 1. 8. A method formanufacturing a silicon carbide film in which a crystal orientation isinherited on a single crystal substrate surface and silicon carbide isallowed to epitaxially grow, the method for manufacturing the siliconcarbide film comprising steps of: entirely or partially providing saidsubstrate surface with a plurality of undulations extended parallel inone direction; and allowing silicon carbide to grow on the substratesurface, wherein said substrate comprises a single crystal Si, thesubstrate surface comprises a (001) surface, and the surface is providedwith the undulation extended in parallel with a [110] orientation.
 9. Amethod for manufacturing a silicon carbide in which a crystalorientation is inherited on a single crystal substrate surface andsilicon carbide is allowed to epitaxially grow, the method comprisingthe steps of: entirely or partially providing said substrate with aplurality of undulations extended parallel in one direction, each ofsaid undulations being formed in a manner such that crests and troughsthereof repeatedly appear when viewed from a direction where saidundulations extend in parallel, each crest has an inclined surface witha predetermined angle relative to a basal plane, and the inclinedsurfaces forming adjacent crests are opposed to each other withdisposing the trough therebetween; and allowing the silicon carbide togrow on the substrate surface.